EP 1 743 225 B1 discloses a master/reserve (standby) configuration for an automation system for controlling a technical process, such as the production of energy.
In this case, a master system (master) is connected by means of a fast physical communication link, an Ethernet, to a standby or reserve system (reserve) (redundant master/reserve configuration), with the fast communication link being used to bidirectionally interchange data—typically in the form of data packets on the basis of a standardized transmission protocol and typically once per automation cycle—between the master and the reserve.
A redundant master/reserve system of this type with time-critical tasks, as in the case of the automation system here, requires, particularly in the case of the automation system, specifically for the energy production process, an efficient, reliable, controllable or controlled and deterministic communication mechanism for the bidirectional interchange of data between the master and the reserve.
In this context, essential demands on the data interchange are, in detail:    a) reliable, controlled or controllable and robust operation with deterministic transmission times,    b) bidirectional data interchange (full duplex),    c) short or reduced transfer times,    e) efficient use of existent resources, such as computation time and the like, and communication bandwidth,    f) support for point-to-point connections,    g) use of standardized transmission protocols, e.g. Ethernet.
It is also known practice to implement data interchange between communication subscribers/appliances in a networked system on the basis of TCP/IP or similar communication protocols in accordance with layer 4 or above based on an OSI layer or OSI reference model.
Although standard communication protocols of this type at user level adopt control of transport, for example, by means of constant interchange of appropriate control messages such as acknowledgement messages, in the system, they have a complex and elaborate protocol stack and are not deterministic.
Furthermore, data interchange proceeding on the basis of these mechanisms requires long transmission or transfer times, and in this case a total transfer time for bidirectional data interchange between two communication subscribers is obtained by adding up the transfer times for both directions between the communication subscribers.
Although various realtime expansions for the data transmission address deterministic transmission times, in this case too, the total transfer time is obtained by adding up the transfer times for the two directions between the communication subscribers. Real time expansions also necessitate a relatively high level of management expenditure in the system, have repercussions on the system and thus also make no kind of improvements in terms of transfer time and efficiency.